The invention relates generally to user input for computer systems and more particularly to a touch and force-sensitive back-side interface for hand-held electronic devices (e.g., hand-held electronic and computer platforms).
An increasingly popular form of electronic device is the hand-held multi-media device. Illustrative devices of this type include palm or hand-held personal computers, tablet computer systems, mobile telephones, personal digital assistants, portable video players and portable audio players. One specific example of such a device is the video iPod® from Apple Computer. (IPOD is a registered trademark of Apple Computer, Inc.) In this class of device the display screen, typically a liquid crystal display (“LCD”), is often to small to make effective use of finger based touch input. Although a touch-screen interface could be embedded in or overlaid on the display, the use of even a single finger for input may occlude a significant portion of the display or cover more than a single operational control element. While this problem could be mitigated by limiting the touch area to a portion of the display screen (e.g., the display edges where horizontal or vertical motion could emulate slider controls), a single finger could still cover a substantial amount of the useful display area. In addition, display smudging is a problem as with all finger sensitive touch-screen interfaces. While stylus based touch-screens may be used to partially reduce the occluding problem and eliminate smudging, they suffer a large disadvantage compared to finger based touch-screen systems in that they require the storage and removal of a stylus. In addition, for small hand-held devices a stylus input requires the use of two hands: one to hold the device and one to hold and manipulate the stylus.